I just hooked up my tuner pro today.....but I dont know what kind of cable to use for the utec and tuner to communicate. Any help would be appreciated.

RS232 db9 female to db9 male

were can i buy this cable? Radio Shack?

Yep.. basically its the same cable that connects the UTEC to your computer.. in fact you should have gotten a cable with both your UTEC and your Tuner.. so you just use one from it.. If not.. just get a regular DB9M to DB9F cable from radio shack or CompUSA

Is the knock sensor the only difference between the tuner pro and the tuner regular?

No, there are some extra connectors that tuner lite doesn't have as well.

I think there's 4 inputs and 2 outputs that the tuner pro has, that the tuner doesn't.

Radio Shack is just about the only place to get this cable without ordering it online. I went to Circuit City, Comp USA, Best Buy, Staples, Office Max etc... No one stocks this cable anymore.